Astronomy and Astrophysics, volume 540, L9-9 (2012/4-1)
An upper limit to the variation in the fundamental constants at redshift z = 5.2.
LEVSHAKOV S.A., COMBES F., BOONE F., AGAFONOVA I.I., REIMERS D. and KOZLOV M.G.
Abstract (from CDS):
We constrain a hypothetical variation in the fundamental physical constants over the course of cosmic time. We use unique observations of the CO(7-6) rotational line and the [CI] 3P2-3P1 fine-structure line towards a lensed galaxy at redshift z=5.2 to constrain temporal variations in the constant F=α2/µ, where µ is the electron-to-proton mass ratio and α is the fine-structure constant. The relative change in F between z=0 and z=5.2, ΔF/F=(Fobs-Flab)/Flab, is estimated from the radial velocity offset, ΔV=Vrot-Vfs, between the rotational transitions in carbon monoxide and the fine-structure transition in atomic carbon. We find a conservative value ΔV=(1±5)km/s (1σC.L.), which when interpreted in terms of ΔF/F gives ΔF/F<2x10–5. Independent methods restrict the µ-variations at the level of Δµ/µ<1x10–7 at z=0.7 (look-back time tz0.7=6.4Gyr). Assuming that temporal variations in µ, if any, are linear, this leads to an upper limit on Δµ/µ<2x10–7 at z=5.2 (tz5.2=12.9Gyr). From both constraints on ΔF/F and Δµ/µ, one obtains for the relative change in α the estimate Δα/α<8x10–6, which is at present the tightest limit on Δα/α at early cosmological epochs.
elementary particles - line: profiles - techniques: radial velocities - galaxies: high-redshift
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